JP4962135B2 - Image forming apparatus and image density correction method - Google Patents

Description

  The present invention relates to an image forming apparatus and an image that can be applied to a color printer, a color copying machine, a multi-function peripheral, and the like that detect and correct the density of the image when forming an image on special paper such as a postcard or an envelope. The present invention relates to a density correction method.

  Conventionally, a color copying machine often controls density correction by detecting the image density of a sheet after toner fixing in order to perform image density correction. For example, a density patch is printed on a sheet for every predetermined number of printed sheets, and the density is detected by a color sensor. In this case, in order to confirm the print density set in the print JOB operation, it is generally performed to print a density patch on a sheet to be passed through the print JOB operation and confirm the density.

  In connection with such a conventional example, Patent Document 1 discloses a color image forming apparatus. According to this color image forming apparatus, the first correction table for keeping the toner amount constant and the second correction table for keeping the chromaticity constant are provided by the user according to the image forming conditions. The first or second correction table is selected. Thereby, an image having a desired color characteristic can be obtained.

  Patent Document 2 discloses a color image forming apparatus. According to this color image forming apparatus, whether the light reflection characteristics of the toner patch formed on the transfer belt is detected by the density sensor and whether or not the image density control using the color sensor is performed according to the detection result is determined. Is to judge. As a result, the number of executions of image density control using a color sensor is reduced, and good density stability can be obtained while suppressing an increase in waiting time for image formation and image formation cost.

Japanese Patent Laying-Open No. 2005-321567 (page 9, FIG. 6) Japanese Patent Laying-Open No. 2005-321572 (page 9, FIG. 8)

  However, when correcting the image density of special shape paper such as envelopes and business cards, the color copying machine according to the conventional example exceeds the print range of the special shape paper because the density patch print range exceeds the entire density patch. The tone may not be printed on specially shaped paper. Further, when correcting the image density of difficult special paper or expensive special paper such as a postcard, the density patch is printed on the special paper for density check, which is wasteful. In this case, the printing paper for confirming the image density is not limited to any paper, and the density changes depending on the paper color, reflectance (glossiness / roughness), moisture absorption, etc. It is necessary to print density patches on paper suitable for the above.

  Further, according to Patent Document 1 related to the conventional example, the image density of a special paper such as a postcard is detected by the first and second correction information even if an image having a color characteristic suitable for the user's preference can be formed. When obtaining correction information, it is necessary to detect the density using expensive special paper.

  According to Patent Document 2, even if the number of executions of image density control can be reduced, when detecting the image density of a special paper such as a postcard, it is necessary to detect the density using an expensive special paper.

  Therefore, in order to solve such a problem related to the conventional example, when detecting the image density of a special paper such as a postcard, the density is determined using an inexpensive normal paper without using an expensive special paper. It is an object of the present invention to provide an image forming apparatus and an image density correction method that enable detection and maintain the same density detection accuracy as that of special paper.

  In order to solve the above-described problem, an image forming apparatus according to claim 1 performs an operation of forming an image for density detection on a sheet and correcting the image density based on the image formed on the sheet. Image forming means for forming an image, a paper storage section for storing paper to be supplied to the image forming means, paper type information indicating the type of paper stored in the paper storage section, and Setting means for associating and setting storage unit identification information for identifying a paper storage unit, input means for inputting paper selection information for selecting a sheet on which the image for density detection is to be input, and When the density correction mode is executed, the sheet selection information input from the input unit is compared with the sheet type information set from the setting unit, and the sheet type information matched with the sheet selection information is correlated. It is characterized in that a control means for determining the sheet accommodating portion from the receiving portion identification information.

  According to the image forming apparatus of the first aspect, when the density correction mode is executed, the control unit collates the sheet selection information with the sheet type information and associates the sheet selection information with the sheet type information that matches the sheet selection information. The paper storage unit is determined from the storage unit identification information. Thereby, an image for density detection can be formed on the paper stored in the determined paper storage unit. Therefore, when detecting the image density of a special paper such as a postcard or an envelope, the density can be detected using an image formed on an inexpensive ordinary paper without using an expensive special paper.

  An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect, wherein the paper selection information includes at least one of plain paper, recycled paper, backing paper, the amount of glazing, glossiness, and color. It is what.

  According to a third aspect of the present invention, there is provided an image forming apparatus according to the first aspect, comprising a plurality of paper storage portions, wherein the plurality of paper storage portions include plain paper, recycled paper, backing paper, paper amount of gloss, gloss or color. The paper to be shown is accommodated.

  According to a fourth aspect of the present invention, there is provided an image forming apparatus according to the first aspect, further comprising a detection unit that detects an image for density detection formed on the paper by the image forming unit, and the control unit is based on a detection signal from the detection unit. Thus, the image density is corrected.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, the image forming apparatus includes a storage unit that stores the paper type information and the storage unit identification information in association with each other.

  According to a sixth aspect of the present invention, there is provided an image forming apparatus configured to form an image for density detection on a sheet and store the image in the sheet storage unit when the operation for correcting the image density based on the image formed on the sheet is set to the density correction mode. Acquiring the sheet type information indicating the type of the sheet that has been received, the storage unit identification information for identifying the paper storage unit, and storing the acquired paper type information and the storage unit identification information in association with each other A step of acquiring sheet selection information for selecting a sheet on which the density detection image is to be formed when the density correction mode is executed; the acquired sheet selection information; and the stored sheet type Checking the information, determining the paper storage unit from the storage unit identification information associated with the paper type information that matches the paper selection information, and determining the paper storage The paper housed in, is characterized in that a step of detecting and correcting the concentration step and the formed image for the density detection to form an image for density detection.

  According to the image forming apparatus according to claim 1 and the image density correction method according to claim 6, paper selection information for selecting a paper on which a density detection image is to be formed and a paper type when executing the density correction mode. And the paper storage unit is determined from the storage unit identification information associated with the paper type information that matches the paper selection information.

  With this configuration, it is possible to form an image for density detection on the paper stored in the paper storage unit determined based on the paper selection information. As a result, when detecting the image density of special paper such as postcards and envelopes, it is possible to detect the density using cheap normal paper without using expensive special paper, and at the same level as special paper. The accuracy of density detection can be maintained. Accordingly, the density correction can be performed based on the image density detected with low cost and high accuracy.

  According to the image forming apparatus of the second aspect, the image for density detection is formed based on at least one of the plain paper, the recycled paper, the back paper, the amount of haze, the glossiness, and the color information. The paper can be selected.

  According to the image forming apparatus of the third aspect, the density detection image is printed on the plain paper, the recycled paper, the back paper, the paper amount indicating the amount of gloss, the glossiness, or the color stored in the plurality of paper storage units. Can be formed.

  According to the image forming apparatus of the fourth aspect, it is possible to detect the color image for density detection formed on the paper.

  According to the image forming apparatus of the fifth aspect, the paper storage unit can be determined based on the paper type information and the storage unit identification information stored in association with the storage unit.

  Subsequently, embodiments of an image forming apparatus and an image density correction method according to the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram showing a configuration example of a color image forming apparatus 100 as an embodiment according to the present invention. A tandem color image forming apparatus 100 shown in FIG. 1 constitutes an example of an image forming apparatus. When an image is formed on special paper such as a postcard or an envelope, the density of the image is detected and corrected. is there.

  The basic operation of the color image forming apparatus 100 is based on digital color image information, and allows a plurality of photosensitive drums 1Y, 1M, 1C, and 1K to pass through a rotation transmission mechanism (not shown) and a common motor (drive source). After driving, the color images formed by the respective photosensitive drums 1Y, 1M, 1C, and 1K are superimposed on the intermediate transfer belt 6, and the color images are transferred to a predetermined sheet and fixed.

  The above-described color image information is output from the document reading unit 102 shown in FIG. For example, the document reading unit 102 includes an automatic document feeder (ADF) (not shown) and a document image scanning exposure device. In this example, the document placed on the ADF document table is conveyed by the conveying means, the image surface of the document is scanned and exposed by the optical system of the document image scanning exposure apparatus, and the image information is read from the document by the CCD imaging device. The image signal obtained in this way is output. The image signal photoelectrically converted by the CCD image pickup device is subjected to A / D conversion, shading correction and the like in an image processing means (not shown), and digital color image information R-DATA, G-DATA, and B-DATA (hereinafter, referred to as “image data”) Simply referred to as image data R, G, B). Thereafter, the image data R, G, and B undergo predetermined image processing. The image forming data Y, M, C, and BK after the image processing is output to the image forming unit 80.

  The image forming unit 80 constitutes an example of an image forming unit, and includes an image forming unit 10Y having a yellow (Y) photosensitive drum 1Y and an image forming unit 10M having a magenta (M) photosensitive drum 1M. An image forming unit 10C having a cyan (C) photosensitive drum 1C, an image forming unit 10K having a black (K) photosensitive drum 1K, and an endless intermediate transfer belt 6. It is prepared for. In the image forming unit 80, image formation processing is performed for each of the photosensitive drums 1Y, 1M, 1C, and 1K, and the toner images of the respective colors that are image-processed by the photosensitive drums 1Y, 1M, 1C, and 1K of the respective colors. They are superimposed on the intermediate transfer belt 6 to form a color image.

  In this example, the image forming unit 10Y includes a charger 2Y, a line-shaped optical head (hereinafter referred to as LPH unit 5Y), a developing unit 4Y, and a cleaning for an image forming body in addition to the photosensitive drum 1Y. Means 8Y is provided to form a yellow (Y) color image. For example, the photosensitive drum 1Y is rotatably provided near the upper right portion of the intermediate transfer belt 6 so as to form a Y-color toner image. In this example, the photosensitive drum 1Y is rotated counterclockwise. A charger 2Y is provided on the lower right side of the photosensitive drum 1Y so as to charge the surface of the photosensitive drum 1Y to a predetermined potential.

  An LPH unit 5Y is provided almost directly beside the photosensitive drum 1Y, and has a predetermined strength based on the image data for Y color with respect to the previously charged photosensitive drum 1Y. A laser beam is irradiated at once. As the LPH unit 5Y, an LED (Light Emitting Diode) head (not shown) arranged in a line is used. For the image writing system, a scanning exposure system using a polygon mirror (not shown) may be used instead of the LPH unit. An electrostatic latent image for Y color is formed on the photosensitive drum 1Y.

  A developing unit 4Y is provided above the LPH unit 5Y, and operates to develop a Y-color electrostatic latent image formed on the photosensitive drum 1Y. The developing unit 4Y has a Y-color developing roller (not shown). In the developing unit 4Y, a Y color toner agent and a carrier are stored.

  The Y-color developing roller has a magnet disposed therein, and rotates and conveys the two-component developer obtained by stirring the carrier and the Y-color toner agent in the developing unit 4Y to the opposite part of the photosensitive drum 1Y. The electrostatic latent image is developed by the color toner agent. The Y color toner image formed on the photosensitive drum 1Y is transferred to the intermediate transfer belt 6 by operating the primary transfer roller 7Y (primary transfer). A cleaning unit 8Y is provided below the left side of the photosensitive drum 1Y so as to remove (clean) the toner agent remaining on the photosensitive drum 1Y in the previous writing.

  In this example, an image forming unit 10M is provided below the image forming unit 10Y. The image forming unit 10M includes a photosensitive drum 1M, a charger 2M, an LPH unit 5M, a developing unit 4M, and an image forming member cleaning unit 8M, and forms a magenta (M) color image. . An image forming unit 10C is provided below the image forming unit 10M. The image forming unit 10C includes a photosensitive drum 1C, a charger 2C, an LPH unit 5C, a developing unit 4C, and a cleaning unit 8C for an image forming body, and forms a cyan (C) color image. .

  An image forming unit 10K is provided below the image forming unit 10C. The image forming unit 10K includes a photosensitive drum 1K, a charger 2K, an LPH unit 5K, a developing unit 4K, and an image forming member cleaning unit 8K, and forms a black (BK) image. .

  An organic photoconductor (OPC) drum is used as the photoconductor drums 1Y, 1M, 1C, and 1K. The functions of the members of the image forming units 10M to 10K can be applied by replacing Y with M, C, and K for the same reference numerals of the image forming unit 10Y, and the description thereof will be omitted. A primary transfer bias voltage having a polarity opposite to that of the toner agent to be used (positive polarity in this embodiment) is applied to the primary transfer rollers 7Y, 7M, 7C, and 7K.

  The intermediate transfer belt 6 superimposes the toner images transferred by the primary transfer rollers 7Y, 7M, 7C and 7K to form a color toner image (color image). The color image formed on the intermediate transfer belt 6 is conveyed toward the secondary transfer roller 7A as the intermediate transfer belt 6 rotates clockwise. The secondary transfer roller 7A is located below the intermediate transfer belt 6 and transfers the color toner image formed on the intermediate transfer belt 6 onto a sheet of paper (secondary transfer).

  In this example, a cleaning unit 8A is provided above the left side of the intermediate transfer belt 6 and operates to clean the toner agent remaining on the intermediate transfer belt 6 after transfer. The cleaning unit 8 </ b> A has a neutralization unit (not shown) that neutralizes the charge on the intermediate transfer belt 6 and a pad that removes toner and the like remaining on the intermediate transfer belt 6. The intermediate transfer belt 6 after the belt surface is cleaned by the cleaning unit 8A and discharged by the discharging unit enters the next image forming cycle. As a result, a color image can be formed on the paper.

  The color image forming apparatus 100 includes a sheet feeding unit 20 and a fixing unit 17 in addition to the image forming unit 80. The paper feeding unit 20 includes paper feeding trays T1 to T4 and a manual paper feeding tray T5. This manual paper feed tray T5 is disposed below the image forming unit 10K. Paper feed trays T1 to T4 are arranged below the manual paper feed tray T5. These trays T1 to T5 constitute an example of a sheet storage unit.

  In this example, various types of paper are stored in each paper feed tray. For example, A4-size ordinary paper P1 is stored in the paper feed tray T1. Further, the paper feed tray T2 accommodates a paper sheet P2 indicating the gloss level “dull”. Here, the glossiness of a sheet having a blank sheet glossiness of, for example, a value greater than 65% is referred to as “gross”, and the glossiness of a sheet having a blank sheet glossiness of 65% or less and a value of 30% or more is represented as “dull”. In other words, the glossiness of a paper having a blank paper glossiness value smaller than 30% is referred to as “matte”.

  The paper feed tray T3 accommodates paper P3 having a reed amount (continuous amount) “28.5 kg”, and the paper feed tray T4 contains paper P4 indicating a reed amount “35.0 kg” and “yellow”. A yellow envelope P5 indicating special paper is accommodated in the paper feed tray T5. Here, the special paper includes, for example, a business card, a postcard, and a photograph in addition to the envelope. The special paper includes paper having a shape in which the density patch cannot be printed.

  In this example, when the density of the printed image of the envelope P5 accommodated in the manual paper feed tray T5 is detected and corrected, for example, the amounts “35.0 kg” and “yellow” accommodated in the paper feed tray T4 are set. The sheet P4 shown is selected and used. As described above, when correcting the density of the print image of the envelope P5, the operation panel 30 is installed above the image forming unit 10Y in order to select the paper P4 stored in the paper feed tray T4. The operation panel 30 functions as an example of a setting unit and an input unit.

  For example, the user accommodates the paper P4 indicating the weight “35.0 kg” and “yellow” in the paper feed tray T4. At this time, the user operates the operation panel 30 to select the tray selection information (container identification information) for identifying the paper feed tray T4, and the paper type information indicating the amount of “35.0 kg” and “yellow”. Associate and set. After the setting, when detecting and correcting the density of the print image of the envelope P5, the user sets the density correction mode from the operation panel 30 and selects the paper on which the density detection image (density patch image) is to be formed. For example, “yellow” is input as paper selection information. Here, the density correction mode refers to an operation of forming an image for density detection on a sheet and correcting the image density based on the image formed on the sheet.

  In this example, when the density of the print image of the envelope P5 is detected and corrected, the paper feed tray T4 associated with the paper type information “yellow” is selected and the paper P4 stored in the paper feed tray T4 is selected. A density patch image is printed. Therefore, when detecting the image density of a special paper such as the envelope P5, the density can be detected using an inexpensive normal paper P4 without using an expensive special paper, and at the same density as the special paper. The accuracy of detection can be maintained.

  In addition, the sheet feeding unit 20 includes sending rollers 21A to 21E, conveying rollers 22A to 22D, and registration rollers 23 on a sheet conveying path from each sheet feeding tray to the secondary transfer roller 7A. The delivery roller 21A is installed in the vicinity of the paper discharge outlet of the paper feed tray T1, and feeds the paper P1 stored in the paper feed tray T1 toward the transport roller 22A. The transport roller 22A receives the fed paper P1 and transports the paper P1 toward the registration roller 23. The registration roller 23 is installed in the vicinity of the secondary transfer roller 7A, and once holds the paper P1 conveyed by the conveyance roller 22A in front of the secondary transfer roller 7A, toward the secondary transfer roller 7A in accordance with the image timing. It is made to send out.

  Similarly, the delivery roller 21B is installed in the vicinity of the paper discharge opening of the paper feed tray T2, and feeds the paper P2 stored in the paper feed tray T2 toward the transport roller 22B. The transport roller 22B receives the sent paper P2, and transports the paper P2 toward the transport roller 22A. Further, the delivery roller 21C is installed in the vicinity of the paper discharge outlet of the paper feed tray T3, and feeds the paper P3 stored in the paper feed tray T3 toward the transport roller 22C. The transport roller 22C receives the sent paper P3 and transports the paper P3 toward the transport roller 22B described above. Further, the delivery roller 21D is installed in the vicinity of the paper discharge outlet of the paper feed tray T4, and feeds the paper P4 stored in the paper feed tray T4 toward the transport roller 22D. The transport roller 22D receives the fed paper P4 and transports the paper P4 toward the transport roller 22C described above. The delivery roller 21E is installed in the vicinity of the paper discharge outlet of the paper feed tray T5, and sends the envelope P5 accommodated in the paper feed tray T5 toward the registration roller 23. In this way, the sheets P1 to P4 and the envelope P5, which are special sheets, stored in each sheet feed tray are sent out from the corresponding sheet feed tray toward the secondary transfer roller 7A.

  The secondary transfer roller 7A is configured to transfer the color image carried on the intermediate transfer belt 6 onto a predetermined sheet whose sheet conveyance is controlled by the registration roller 23.

  A fixing unit 17 is provided on the downstream side of the above-described secondary transfer roller 7A to fix the paper on which the color image has been transferred. The fixing unit 17 includes a fixing roller 17A, a pressure roller 17B, a fixing cleaning unit 17C, a heating (IH) heater (not shown), and the like. In the fixing process, the sheet is heated and pressed by passing the sheet between the fixing roller 17A and the pressure roller 17B heated by the heater. As a result, the toner transferred onto the paper is fixed on the paper. The fixing cleaning unit 17C removes (cleans) the toner agent remaining on the fixing roller 17A and the like.

  On the downstream side of the fixing unit 17, paper discharge rollers 24A and 24B, a paper passage sensor 25, and a color sensor 26 are provided. The paper passage sensor 25 is installed in the vicinity of the fixing unit 17, detects the passage of the paper after toner fixing sent from the fixing unit 17, and supplies the digitized paper detection information PD shown in FIG. 3 to the control unit 50. Output. As the paper passage sensor 25, for example, a reflection type photosensor using a photo IC (Integrated Circuit) as a light receiving element is used.

  The paper discharge rollers 24A and 24B pinch the paper detected by the paper passage sensor 25 and discharge the paper onto a paper discharge tray (not shown) outside the apparatus. The color sensor 26 functions as an example of a detection unit, and is installed between the paper discharge rollers 24A and 24B. The color sensor 26 detects the image of the paper on which the density patch image is printed in the density correction mode. As the color sensor 26, for example, a sensor incorporating an RGB LED light source is used.

  Next, a tray-paper type association table 40 in which the above-described tray selection information and paper type information are associated will be described. FIG. 2 is an explanatory diagram illustrating a configuration example of the association table 40. Items “tray T1” to “tray T5” are set in the vertical items of the association table 40 shown in FIG. These items correspond to the paper feed trays T1 to T4 and the manual paper feed tray T5 shown in FIG. In addition, the item “plain paper”, the item “recycled paper”, the item “back paper”, the item “light amount (kg)”, the item “glossiness”, and the item “color” are set in the horizontal items of the related table 40. ing. In this example, the contents of these items in the horizontal item serve as a determination criterion when selecting a sheet to be used when detecting the image density.

  In this example, in the item “tray T4”, data “35.0” is set in the item “weight (kg)”, and data “yellow” is set in the item “color”. This means that the paper feed tray T4 contains yellow paper with a weight of 35.0 kg. These data are input from the operation panel 30 of FIG.

  In the item “tray T1”, data “1” is set in the item “plain paper”, and data “white” is set in the item “color”. This means that white plain paper is stored in the paper feed tray T1.

  In the item “tray T2”, data “Dal” is set in the item “glossiness”. This means that the paper feed tray T2 contains paper whose glossiness is dull. In addition, in the item “tray T3”, data “28.5” is set in the item “weight (kg)”. This means that the paper tray T3 contains paper having a droop amount of 28.5 kg. In the item “tray T5”, no data is set. This is because in this example, the manual feed tray T5 indicated by the item “tray T5” contains an envelope P5 which is a special sheet, and the density patch image is not printed on the envelope P5.

  The data “−” set in the association table 40 means that no data is set, that is, data “0”. This association table 40 is initialized and cleared to zero when the color image forming apparatus 100 is shipped.

  FIG. 3 is a block diagram illustrating a configuration example of a control system of the color image forming apparatus 100. The control system of the color image forming apparatus 100 shown in FIG. 3 includes a control unit 50 and an image memory 31. The control unit 50 functions as an example of a control unit and includes a system bus 55. The system bus 55 includes an I / O port 54, an EEPROM (Electrically Erasable and Programmable Read Only Memory) 53, and a RAM (Random Access). A memory 52 and a CPU (central processing unit) 51 are connected.

  The EEPROM 53 constitutes an example of a storage unit, and the EEPROM 53 stores the tray-paper type relation table 40 shown in FIG. Further, the EEPROM 53 prints the density patch on the paper, irradiates the paper with light by the color sensor 26 to detect the image on the paper, and controls the operation for correcting the density of the print image based on the image. A correction control program is stored. The CPU 51 reads the correction control program from the EEPROM 53 and develops it in the RAM 52. The RAM 52 is used as a work memory by developing a correction control program and the like.

  An operation panel 30 is connected to the CPU 51. The operation panel 30 includes a touch panel 30A and a numeric keypad 30B.

  In this example, the touch panel 30 </ b> A and the numeric keypad 30 </ b> B are operated by the user, and operation information OPD including tray selection information for identifying the paper feed tray and paper type information indicating the paper type is output to the CPU 51. For example, operation information OPD including tray selection information indicating the paper feed tray T4 and paper type information indicating the amount of “35.0 kg” and “yellow” is output to the CPU 51. The CPU 51 refers to the related table 40 stored in the EEPROM 53, and sets data “35.0” in the field “item (kg)” related to the item “tray T4” of the related table 40. Further, the CPU 51 sets the data “yellow” in the item “color” column relating to the item “tray T4”, and stores the tray selection information and the paper type information in association with each other.

  After the storage, for example, 1000 envelopes P5 accommodated in the manual feed tray T5 shown in FIG. 1 are set to be printed. In this example, it is assumed that the density of the printed image is corrected when 500 sheets are printed. Of course, the number is not limited to 500, and may be every 300 or 700. By the user operating the touch panel 30A, the density correction mode is selected, and operation information OPD in which, for example, “yellow” is selected as paper selection information for selecting the paper on which the density patch image is formed is output to the CPU 51. .

  Thereafter, when printing of the envelope P5 is started, image information is read from the document by the document image scanning exposure apparatus of the document reading unit 102 described above to obtain a photoelectrically converted image signal. This image signal is subjected to A / D conversion, shading correction, and the like in image processing means (not shown), and becomes digital image data R, G, B. Thereafter, the image data R, G, and B undergo predetermined image processing. The image forming data Y, M, C, and BK for Y, M, C, and BK after image processing are output to the image memory 31.

  For example, the CPU 51 controls to output the Y-color image formation data Y of the image memory 31 to the LPH unit 5Y of the image forming unit 80. The LPH unit 5Y is controlled by the CPU 51 so as to collectively irradiate the pre-charged photosensitive drum 1Y with a laser beam having a predetermined intensity based on the Y-color image formation image data Y. Thereafter, the Y-color electrostatic latent image formed on the photosensitive drum 1Y is developed with the Y-color toner agent, and undergoes the above-described primary transfer.

  The CPU 51 drives and controls the registration roller 23 of the paper feeding unit 20, temporarily holds the envelope P5 sent out by the sending roller 21E shown in FIG. 1 in front of the secondary transfer roller 7A, and matches the image timing. It sends out toward the secondary transfer roller 7A. Thereafter, the secondary transfer and fixing processes described above are performed.

  After fixing, the paper passage sensor 25 detects the passage of the envelope P5 sent from the fixing unit 17 after toner fixing, and outputs paper detection information PD to the CPU 51. For example, the CPU 51 counts the number of printed sheets based on the sheet detection information PD. In this example, the CPU 51 starts the image density correction process when the count value exceeds “500”. For example, the CPU 51 first controls the image forming unit 80 so as to form a predetermined density patch. Next, in order to select a sheet on which the density patch image is to be formed, the CPU 51 sequentially selects “yellow” of the input sheet selection information and data set in the item “color” column of the related table 40. Collate. For example, the CPU 51 first collates the data “white” of the item “tray T1” of the association table 40 with “yellow” of the paper selection information. After the collation, the CPU 51 determines that they do not match, and next refers to the item “color” of the item “tray T2” to determine that the data is zero and does not perform collation. Next, the data “yellow” of the item “color” of the item “tray T4” is collated with “yellow” of the paper selection information. After collation, the CPU 51 determines that they match, and controls to select the yellow paper P4 stored in the paper feed tray T4.

  For example, the CPU 51 controls to stop the feed roller 21E of the paper feed unit 20 that feeds the envelope P5 stored in the manual feed tray T5. Thereby, conveyance of envelope P5 stops. Subsequently, the CPU 51 drives and controls the feed roller 21D of the paper feed unit 20 in order to send out the paper P4 stored in the selected paper feed tray T4. As a result, the paper P4 is sent out from the paper feed tray T4 toward the transport roller 22D. Further, the CPU 51 drives and controls the conveyance rollers 22D, 22C, 22B, and 22A, and conveys the paper P4 toward the registration roller 23.

  The registration roller 23 is controlled by the CPU 51 so as to temporarily hold the sheet P4 conveyed by the conveyance roller 22A in front of the secondary transfer roller 7A and send it toward the secondary transfer roller 7A in accordance with the image timing. Thereafter, the density patch is secondarily transferred to the paper P4 and the fixing process is performed. In this manner, the image forming unit 80 transfers and fixes the density patch on the paper P4 selected by the CPU 51 to form an image. As a result, when detecting the image density of a special paper such as the envelope P5, the density can be detected using an inexpensive normal paper P4 without using an expensive special paper, and at the same level as the special paper. The accuracy of density detection can be maintained.

  After fixing, the paper passage sensor 25 detects the passage of the paper P4 after toner fixing sent out from the fixing unit 17 and outputs paper detection information PD to the CPU 51. When this paper detection information PD is input, the CPU 51 drives and controls the color sensor 26. The color sensor 26 emits RGB LED light for the density patch image fixed on the paper P4, and receives the reflected light from the paper P4 to detect the image. The color sensor 26 outputs the detected density detection information DD to the CPU 51 via the I / O port 54.

  The CPU 51 corrects the image density based on the density detection information DD. For example, the CPU 51 compares the density patch data indicated by the density detection information DD with the density patch data (target density) used to record the density patch for each density patch. After the comparison, when there is a difference between the density patch data indicated by the density detection information DD and the target density, the CPU 51 forms an image to correct the density of the density patch data to the target density (tone correction). The conveyance of the two-component developer of the unit 80, the drum potential, the fixing temperature, and the like are controlled. In this way, the sheet on which the density patch image is printed is selected to correct the image density.

  Next, the configuration and operation example of the operation panel 30 will be described with reference to FIGS. FIG. 4 is an explanatory diagram illustrating a configuration of an initial screen of the operation panel 30 and an operation example. The numeric keypad 30B of the operation panel 30 shown in FIG. 4 includes numbers “0” to “9” and a symbol “·” indicating a decimal point. Further, on the touch panel 30A of the operation panel 30, a “top screen” HD1 is displayed as an initial screen, and subsequently, a “print start” button BT1, a “print condition designation” button BT2, and a “set / change” button BT3 are displayed. ing. The touch panel (or touch screen) 30A is a device that combines a display monitor, a matrix switch, and the like, and is an input device that operates a device by pressing a display unit on a panel (screen) with a finger or the like.

  When the “print start” button BT1 displayed on the “top screen” HD1 of the touch panel 30A is pressed, operation information OPD indicating the print start is output to the CPU 51 shown in FIG. When the “print condition designation” button BT2 is pressed, the operation information OPD indicating the condition designation for printing the paper is output to the CPU 51, and the “print condition designation screen” HD5 shown in FIG. 8 is displayed on the touch panel 30A. Is done.

  When the “set / change” button BT3 is pressed, for example, operation information OPD indicating a paper type setting for correcting the image density is output to the CPU 51, and a “set / change screen” HD2 shown in FIG. 30A.

  FIG. 5 is an explanatory diagram illustrating a configuration and an operation example of the setting / change screen of the operation panel 30. On the touch panel 30A shown in FIG. 5, the “setting / change” button BT3 in FIG. 4 is pressed, and a “setting / change screen” HD2 is displayed. This “setting / changing screen” HD2 includes a “paper type setting” button BT4, a “XXX setting” buttons BT5 and BT6, and a “return” button BT30.

  When the “return” button BT30 is pressed, the display returns to the “top screen” HD1 shown in FIG. Further, when the “XXXXX” buttons BT5 and BT6 are pressed, a setting screen (not shown) is displayed on the touch panel 30A. When the “paper type setting” button BT4 is pressed, a “paper type setting screen” HD3 shown in FIG. 6 is displayed on the touch panel 30A.

  FIG. 6 is an explanatory diagram showing a configuration and an operation example of the first paper type setting screen of the operation panel 30. On the touch panel 30A shown in FIG. 6, the “paper type setting” button BT4 in FIG. 5 is pressed, and a “paper type setting screen” HD3 is displayed. The “paper type setting screen” HD3 includes a “tray selection” button BT7, a “paper type setting” button BT8, a “return” button BT30, a “setting” button BT31, a “clear” button BT32, and a “to TOP” button 33. It is configured.

  The “tray selection” button BT7 displayed on the touch panel 30A includes tray buttons “tray T1” to “tray T5”. A tray is set by selecting and pressing any one of these tray buttons.

  Further, the “paper type setting” button BT8 includes “plain paper”, “recycled paper”, “back paper”, “weight (kg)”, “glossiness”, and “color” paper type buttons. . By selecting and pressing one or more paper type buttons from these paper type buttons, the paper type is set.

  FIG. 7 is an explanatory diagram illustrating a configuration and an operation example of the second paper type setting screen of the operation panel 30. On the touch panel 30A shown in FIG. 7, the “color type” of the “paper type setting” button BT8 in FIG. 6 is pressed, and a “paper type setting screen” HD4 is displayed. The “paper type setting screen” HD4 includes a “paper color” button BT9, a “glossiness” button BT10, a “return” button BT30, a “setting” button BT31, a “clear” button BT32, and a “to TOP” button 33. Has been.

  The “paper color” button BT9 displayed on the touch panel 30A includes color buttons of “white”, “yellow”, “red”, “blue”, “green”, “black”, and “gray”. The color of the paper is set by selecting and pressing any one of these color buttons.

  Further, the “glossiness” button BT10 includes gloss buttons of “gross”, “dull”, and “matte”. When one of these gloss buttons is selected and pressed, the gloss level of the paper is set.

  Next, with reference to FIGS. 6 and 7, as an example of an operation for associating the tray with the paper type, for example, an example of associating the paper of the paper amount “35.0 kg” and the paper color “yellow” with the paper feed tray T4 will be described. To do. First, the user selects and presses “tray T4” of the “tray selection” button BT7 in FIG. 6 (dotted line square in the figure). Next, the user selects and presses “weight (kg)” of the “paper type setting” button BT8 (dotted line square in the figure). At this time, a cursor for prompting an input blinks in a numerical value input field N1 provided adjacent to the “weight (kg)”. The user presses the numeric keypad 30B and inputs “35.0”, for example. After the input, the user selects and presses the “SET” button BT31.

  After pressing the “SET” button BT31, the operation information OPD including the tray T4 and the weight “35.0 kg” is output from the touch panel 30A to the CPU 51. The CPU 51 sets the data “35.0” in the column “kg (kg)” of “tray T4” of the related table 40 (see FIG. 2) developed from the operation information OPD to the RAM 52. The CPU 51 also sets the data “35.0” in the column “Tray amount (kg)” of “Tray T4” in the related table 40 simultaneously stored in the EEPROM 53. As a result, the setting of the amount “35.0 kg” for the paper feed tray T4 is completed.

  Subsequently, the user selects and presses “color” of the “paper type setting” button BT8. After pressing, a second “paper type setting screen” HD4 shown in FIG. 7 is displayed on the touch panel 30A. The user selects and presses “yellow” of the “paper color” button BT9 on the “paper type setting screen” HD4 (dotted line square in the figure). Thereafter, the user selects and presses the “SET” button BT31. When the “SETTING” button BT31 is pressed, the screen returns to the “PAPER TYPE SETTING SCREEN” HD3 in FIG. Note that, even if the “return” button BT30 is selected and pressed, yellow is selected in the same manner, and the screen returns to the “paper type setting screen” HD3 in FIG.

  After pressing the “SET” button BT31, the operation information OPD including the tray T4 and the color “yellow” is output from the touch panel 30A to the CPU 51. The CPU 51 sets data “yellow” in the “color” column of “tray T4” of the related table 40 developed from the operation information OPD to the RAM 52. At the same time, the CPU 51 sets the data “yellow” in the “color” column of “tray T4” and updates the related table 40 stored in the EEPROM 53 at the same time. This completes the setting of the color “yellow” for the paper feed tray T4. In this way, the tray and the paper type are associated with each other.

  Note that the “clear” button BT32 is pressed to cancel the selection of each button. When returning to one screen, the “return” button BT30 is pressed. When returning to the “top screen” HD1 shown in FIG. 4, the “to TOP” button BT33 is pressed.

  Next, an example will be described in which the operation panel 30 is operated to specify conditions such as the number of sheets actually printed.

  FIG. 8 is an explanatory diagram showing a configuration and an operation example of the print condition designation screen of the operation panel 30. On the touch panel 30A shown in FIG. 8, the “printing condition designation screen” HD5 is displayed by pressing the “printing condition designation” button BT2 of the “top screen” HD1 shown in FIG. This “printing condition designation screen” HD5 includes a “printing number” field BT11, a “paper size” button BT12, a “paper type” button BT13, a “printing mode” button BT14, a “return” button BT30, a “setting” button BT31, and the like. The “clear” button BT32 is configured.

  In the “number of printed sheets” field BT11 displayed on the touch panel 30A, a numerical value input field N2 is provided. In the numerical value input field N2, the number of prints is input from the numeric keypad 30B. The “paper size” button BT12 includes size buttons “A4”, “A3”, and “B5”. By selecting and pressing any one size button from these size buttons, the size of the paper is set.

  The “paper type” button BT13 includes paper type buttons of “plain paper”, “recycled paper”, “back paper”, “postcard”, “envelope”, “business card”, and “photo (E version)”. Has been. A paper type is set by selecting and pressing one of these paper type buttons.

  The “print mode” button BT14 includes “normal mode” and “density correction mode” print operation buttons. By selecting and pressing any one of these print operation buttons, a paper print operation is set. In this example, when the “density correction mode” button of the “print mode” button BT14 is selected and pressed, a “paper type selection screen” HD6 shown in FIG. 9 is displayed on the touch panel 30A.

  FIG. 9 is an explanatory diagram showing a configuration and an operation example of the paper type selection screen of the operation panel 30. On the touch panel 30A shown in FIG. 9, the “density correction mode” button of the “print mode” button BT14 shown in FIG. 8 is pressed, and a “paper type selection screen” HD6 is displayed on the touch panel 30A. Further, on the touch panel 30A, following the “paper type selection screen” HD6, a “paper color” button BT15, a “glossiness” button BT16, a “paper weight (kg)” button BT17, a “return” button BT30, “ A “Clear” button BT32 and a “To TOP” button BT33 are displayed.

  The “paper color” button BT15 displayed on the touch panel 30A includes color buttons of “white”, “yellow”, “red”, “blue”, “green”, “black”, and “gray”. By selecting and pressing any one of these color buttons, the color of the paper is selected.

  The “glossiness” button BT16 includes gloss buttons of “gross”, “dull”, and “matte”. By selecting and pressing any one of these gloss buttons, the gloss level of the paper is selected.

  In addition, the “paper weight (kg)” button BT17 is “-10”, “11-20”, “21-30”, “31-40”, “41-50”, “51-60”, “61”. ˜70 ”,“ 71-80 ”,“ 81-90 ”,“ 91-100 ”,“ 101-110 ”and“ 110 or more ”weight buttons. By selecting and pressing any one of these buttons, the sheet weight is selected.

  Next, an example in which the density correction mode is designated and about 1000 envelopes are printed will be described with reference to FIGS. First, the user presses the “number of printed sheets” column BT11 in FIG. When the “number of printed sheets” field BT11 is pressed, a cursor for prompting input blinks in the numerical value input field N2. The user presses the numeric keypad 30B and inputs “1000”, for example. After the input, the user selects and presses the “SET” button BT31.

  Next, the user selects and presses the “envelope” button of the “paper type” button BT13 (dotted line square in the figure). Subsequently, the user selects and presses the “density correction mode” button of the “print mode” button BT14 (dotted line square in the figure). When the “density correction mode” button is pressed, the “paper type selection screen” HD6 of FIG. 9 is displayed on the touch panel 30A. On this screen HD6, a selection condition for density correction paper is input. For example, the user selects and presses the “yellow” button of the “paper color” button BT15 (broken line square in the figure). As a result, the condition of the paper used for the image density correction is set. Thereafter, the user selects and presses the “return” button BT30. When the “return” button BT30 is pressed, the “printing condition designation screen” HD5 in FIG. 8 is displayed again. Here, the user presses the “SET” button BT31 to determine the paper printing conditions. Subsequently, the user presses the “return” button BT30 to display the “top screen” HD1 in FIG. Note that the “top screen” HD1 in FIG. 4 may be displayed when the “setting” button BT31 is pressed. Subsequently, the user presses a “print start” button BT1 on the “top screen” HD1 in FIG. 4 to start printing.

  For example, when the number of envelopes printed reaches 500 after the start of printing, as described in detail in FIG. 3, yellow paper, which is the paper condition for printing the density patch image input from the touch panel 30A, is selected. The That is, the yellow paper P4 accommodated in the paper feed tray T4 shown in FIG. 1 is selected, and the density patch is printed on the paper P4. Thereafter, the image of the paper P4 is detected by the color sensor 26, and a predetermined correction process is performed. After the density correction processing, envelopes are continuously printed from the 501st sheet to the 1000th sheet. Thus, when the image density correction is performed, the density correction process can be performed using the inexpensive paper P4 without stopping the color image forming apparatus 100 halfway. Accordingly, the throughput of the print job can be improved.

  FIG. 10 is a flowchart illustrating an operation example of the control system of the color image forming apparatus 100. The paper feed trays T1 to T4 of the color image forming apparatus 100 contain the corresponding papers P1 to P4, and the manual paper feed tray T5 contains the envelope P5. Further, the operation panel 30 is operated by the user, and the tray-paper type relation table 40 shown in FIG. 2 is created and stored in the EEPROM 53. A power supply (not shown) of the color image forming apparatus 100 is turned on, and the correction control program is read from the EEPROM 53 by the CPU 51 and developed in the RAM 52. In this example, 1000 envelopes are printed in the density correction mode, and image density correction processing is performed when the number of printed sheets reaches 500.

  With these as conditions for image density correction at the time of printing, the type of paper and the print mode are set in step ST1 shown in FIG. For example, the user presses the “print condition designation” button BT2 of the “top screen” HD1 displayed on the touch panel 30A in FIG. 4, and the CPU 51 displays the “print condition designation screen” HD5 in FIG. Here, in order to set the number of prints to 1000, “1000” is entered in the numerical value input field N2 of the “print number” field BT11 of the “print condition designation screen” HD5. Subsequently, the “envelope” button of the “paper type” button BT13 is pressed to set the type of printing paper. Further, the “density correction mode” button of the “print mode” button BT14 is pressed to set the density correction mode. Subsequently, in order to set the condition of the paper used for image density correction, the “yellow” button of the button BT15 of the “paper type selection screen” HD6 in FIG. 9 is pressed. Finally, the “SET” button BT31 in FIG. 8 is pressed, and these pieces of information are temporarily stored in the RAM 52, and the process proceeds to step ST2.

  In step ST2, the CPU 51 determines whether or not the density correction mode is selected in step ST1. When the density correction mode is not selected, that is, when the normal mode is selected, the process proceeds to steps ST14 to ST16, and 1000 sheets of envelopes are printed without performing density correction, and the printing process ends. When the density correction mode is selected, the process proceeds to step ST3.

  In step ST3, the CPU 51 determines whether or not a special paper is selected as the print paper in step ST1. In this example, the special paper includes, for example, an envelope, a business card, a postcard, and a photograph. If no special paper is selected, the process proceeds to ST14 to ST16 described above. If special paper (envelope) is selected, the process proceeds to step ST4.

  In step ST4, the CPU 51 determines a sheet (patch printing sheet) on which the density patch image is printed. In this example, the CPU 51 proceeds to step T40 of the subroutine shown in FIG. FIG. 11 is a flowchart illustrating an example of determining a patch print sheet. At step T40 in FIG. 11, the CPU 51 obtains the paper color “yellow” set as the paper condition to be used for image density correction in step ST1 in FIG. 10, and proceeds to step ST41.

  In step ST41, the CPU 51 determines whether or not the patch printing paper is directly designated by the user. For example, when patch print paper is designated by the user, that is, when tray selection information indicating any of the paper feed trays T1 to T4 is set as the paper selection information on the user designation screen (not shown) of the touch panel 30A. The process proceeds to step ST42.

  In step ST42, the CPU 51 determines the paper stored in the corresponding paper feed tray as the patch print paper, and returns to the main routine of FIG.

  If the user does not specify a patch print sheet in step ST41, the process proceeds to step ST43. In step ST43, the CPU 51 determines whether or not a sheet of the same color as the print sheet exists in the sheet feed trays T1 to T4. For example, the CPU 51 collates the paper color set in the item “color” column of the tray-paper type association table 40 developed in the RAM 52 with the paper color “yellow” set in step ST1. After the collation, the CPU 51 selects “tray T4” associated with the matched paper color “yellow”, and proceeds to step ST44.

  In step ST44, for example, the CPU 51 determines whether or not the size of the paper P4 accommodated in the paper feed tray T4 is a size that enables density patch creation. For example, the CPU 51 has a paper size detection sensor (not shown) in the paper feed tray T4, compares the paper size information output from the paper size detection sensor with the print range of the density patch, and based on the comparison result. judge. If the size of the paper P4 is a size that allows density patches to be created, the process proceeds to step ST45.

  In step ST45, the CPU 51 determines the sheet 4P stored in the sheet feed tray T4 as the patch print sheet, and returns to the main routine of FIG.

  Further, when there is no paper of the same color as the printing paper in the paper feed trays T1 to T4 in the above-described step ST43, or in the above-described step ST44, for example, the paper P4 stored in the paper feed tray T4. If the size is not a density patch creation size, the process proceeds to step ST46.

  In step ST46, the CPU 51 determines whether or not a sheet having the same glossiness as that of the print sheet exists in the sheet feed trays T1 to T4. For example, when the glossiness is set in step ST1, the CPU 51 collates the value set in the item “glossiness” column of the tray-paper type relation table 40 with the glossiness set in step ST1. To do. After the collation, the CPU 51 selects any one of the trays T1 to T4 associated with the matched glossiness, and proceeds to step ST47.

  In step ST47, as in step ST44 described above, the CPU 51 determines whether or not the size of the paper stored in the corresponding paper feed tray is a size that enables density patch creation. If the paper size is a size that enables density patch creation, the process proceeds to step ST48.

  In step ST48, the CPU 51 determines the paper stored in the corresponding paper feed tray as the patch print paper, and returns to the main routine of FIG.

  Further, when there is no paper having the same glossiness as the printing paper in the paper feed trays T1 to T4 in the above-described step ST46, or the size of the paper accommodated in the paper feed tray is set in the above-mentioned step ST47. If the density patch size is not available, the process proceeds to step ST49.

  In step ST49, the CPU 51 determines whether a sheet having the same thickness as the print sheet exists in the sheet feed trays T1 to T4. For example, when the amount of hull is set in step ST1, the CPU 51 collates the value set in the item “wage amount (kg)” of the tray-paper type association table 40 with the amount of hull set in step ST1. To do. After the collation, the CPU 51 selects any one of the trays T1 to T4 associated with the matched amount, and proceeds to step ST50.

  In step ST50, as in step ST44 described above, the CPU 51 determines whether or not the size of the paper stored in the corresponding paper feed tray is a size that enables density patch creation. If the paper size is a size that allows density patches to be created, the process proceeds to step ST51.

  In step ST51, the CPU 51 determines the paper stored in the corresponding paper feed tray as the patch print paper, and returns to the main routine of FIG.

  Further, if there is no sheet having the same thickness as the print sheet in the paper feed trays T1 to T4 in step ST49 described above, or the size of the paper stored in the paper feed tray in step ST50 described above is If the size is not such that a density patch can be created, the process proceeds to step ST52.

  In step ST52, the CPU 51 determines that there is no patch printing paper corresponding to the input condition, and proceeds to step ST53. In step ST53, the CPU 51 controls to display information indicating that there is no corresponding patch printing paper on the screen of the touch panel 30A, determines to use the printing paper as the patch printing paper, and returns to the main routine of FIG. .

  In step ST5 of FIG. 10, the CPU 51 determines whether to use patch printing paper (paper P4 in this example) or printing paper (envelope P5 in this example) as the paper on which the density patch is printed. If it is determined in the subroutine of FIG. 11 that patch print paper is used, the process proceeds to step ST6.

  In step ST6, the CPU 51 controls to start a printing operation. For example, the CPU 51 controls to print “1000” envelopes set in step ST1, and proceeds to step ST7.

  In step ST7, the CPU 51 starts counting the number of printed sheets in order to measure the timing for starting the density patch printing. Subsequently, the process proceeds to step ST8.

  In step ST8, the CPU 51 determines whether or not the printing has been completed. In this example, it is determined whether or not the count value exceeds 1000. When printing is completed, the process proceeds to step ST16. If printing has not ended, the process proceeds to step ST9.

  In step ST9, the CPU 51 determines whether or not the counted number of printed sheets has reached the target number of printed sheets (500 sheets). If the number of printed sheets has not reached 500, the process returns to step ST6 to continue the printing operation. When the number of printed sheets reaches 500, the process proceeds to step ST10.

  In step ST10, the CPU 51 interrupts the operation of feeding paper from the paper feed tray containing the printing paper, and controls to feed the paper from the paper feed tray containing the patch printing paper. For example, the CPU 51 controls to stop the feeding roller 21E (see FIG. 1) of the manual paper feed tray T5 in which the envelope P5 that is printing paper is accommodated. Further, the CPU 51 drives the feed roller 21D installed in the paper feed tray T4 so as to send out the patch print paper determined in the above-described step ST4, that is, the yellow paper P4 accommodated in the paper feed tray T4. Thus, the process proceeds to step ST11.

  In step ST11, the color sensor 26 detects the image of the paper P4 on which the density patch is printed, outputs density detection information DD to the CPU 51, and proceeds to step ST12.

  In step ST12, the CPU 51 corrects the image density based on the input density detection information DD, and proceeds to step ST13. In step ST13, the CPU 51 controls to end the density correction. For example, the CPU 51 controls to stop the delivery roller 21D of the paper feed tray T4 in which the paper P4 that is patch printing paper is accommodated. Further, the CPU 51 controls to drive the feeding roller 21E of the manual paper feed tray T5 in which the envelope P5 which is printing paper is accommodated, and returns to step ST6 to start printing on the envelope P5 from the 501st sheet again.

  When the number of printed sheets reaches 1000 in step ST8 described above, the CPU 51 determines that printing has been completed and proceeds to step ST16. In step ST16, the CPU 51 ends the printing process. For example, the CPU 51 controls to stop the feeding roller 21E of the manual paper feed tray T5 in which the envelope P5 is accommodated. In addition, the photosensitive drum of the image forming unit 80, the intermediate transfer belt 6 and the like are controlled to be stopped, and the printing process is ended.

  As described above, according to the color image forming apparatus 100 and the image density correction method of the present invention, the sheet selection information for selecting the sheet on which the density patch image is printed and the sheet type are displayed when the density correction mode is executed. The paper type information is collated, and the paper feed tray is determined from the tray selection information associated with the paper type information that matches the paper selection information.

  Therefore, the density patch image can be printed on the paper stored in the paper feed tray. As a result, when detecting the image density of special paper such as postcards and envelopes, it is possible to detect the density using cheap normal paper without using expensive special paper, and at the same level as special paper. The accuracy of density detection can be maintained. This makes it possible to correct the density based on the image density detected with low cost and high accuracy.

  INDUSTRIAL APPLICABILITY The present invention is suitable for application to color printers, color copiers, and complex machines that detect and correct image density when forming images on special paper such as postcards and envelopes. .

1 is a schematic diagram illustrating a configuration example of a color image forming apparatus 100 as an embodiment according to the present invention. It is explanatory drawing which shows the structural example of the relation table 40 of a tray-paper type. 2 is a block diagram illustrating a configuration example of a control system of the color image forming apparatus 100. FIG. 4 is an explanatory diagram illustrating a configuration of an initial screen of the operation panel 30 and an operation example. FIG. 4 is an explanatory diagram illustrating a configuration and an operation example of a setting / change screen of the operation panel 30. FIG. 6 is an explanatory diagram illustrating a configuration and an operation example of a first paper type setting screen on the operation panel 30. FIG. 6 is an explanatory diagram illustrating a configuration and an operation example of a second paper type setting screen of the operation panel 30. FIG. FIG. 6 is an explanatory diagram illustrating a configuration and an operation example of a printing condition designation screen of the operation panel 30. 6 is an explanatory diagram illustrating a configuration and an operation example of a paper type selection screen of the operation panel 30. FIG. 3 is a flowchart illustrating an example of an operation of a control system of the color image forming apparatus 100. It is a flowchart which shows the example of determination of patch printing paper.

Explanation of symbols

1Y, 1M, 1C, 1K Photosensitive drums 4Y, 4M, 4C, 4K Development units T1 to T4 Paper feed tray (paper storage unit)
T5 Manual feed tray (paper compartment)
6 Intermediate transfer belt 17 Fixing unit 20 Paper feed unit 26 Color sensor (detection unit)
30 Operation panel (setting means, input means)
30A Touch panel 30B Numeric keypad 50 Control unit (control means)
53 EEPROM (storage unit)
80 Image forming unit (image forming means)

Claims (6)

When an image for density detection is formed on a sheet, and the operation for correcting the image density based on the image formed on the sheet is set to the density correction mode,
An image forming means for forming an image;
A paper storage unit for storing paper to be supplied to the image forming unit;
Setting means for associating and setting paper type information indicating the type of paper stored in the paper storage unit and storage unit identification information for identifying the paper storage unit;
Input means for inputting paper selection information for selecting a paper on which the image for density detection is to be formed;
When the density correction mode is executed, the sheet selection information input from the input unit and the sheet type information set from the setting unit are collated, and the accommodation associated with the sheet type information that matches the sheet selection information. An image forming apparatus comprising: a control unit that determines the sheet storage unit from the section identification information. The paper selection information includes
The image forming apparatus according to claim 1, comprising at least one of plain paper, recycled paper, backing paper, haze, glossiness, and color information. A plurality of the paper storage portions;
In the plurality of paper storage portions,
The image forming apparatus according to claim 1, wherein plain paper, recycled paper, backing paper, paper showing the amount of paper, glossiness, or color is stored. A detection unit for detecting the image for density detection formed on the paper by the image forming unit;
The control means includes
The image forming apparatus according to claim 1, wherein the image density is corrected based on a detection signal from the detection unit.   The image forming apparatus according to claim 1, further comprising a storage unit that stores the sheet type information and the storage unit identification information in association with each other. When an image for density detection is formed on a sheet, and the operation for correcting the image density based on the image formed on the sheet is set to the density correction mode,
Obtaining paper type information indicating the type of paper stored in the paper storage unit and storage unit identification information for identifying the paper storage unit;
Storing the obtained paper type information and the storage unit identification information in association with each other;
Obtaining paper selection information for selecting a paper on which the density detection image is to be formed when the density correction mode is executed;
Collating the acquired paper selection information with the stored paper type information, and determining the paper storage unit from the storage unit identification information associated with the paper type information that matches the paper selection information When,
Forming a density detection image on the paper stored in the determined paper storage unit;
And a step of detecting and correcting the density of the formed density detection image.

Images